Simon Cowell has launched an investigation into recent shock news BGT winners Jules and Matisse used a stunt dog in their final show, as it's claimed "heads could roll".

The revelation that a lookalike dog was used to walk the parallel ropes in the final sparked around 500 complaints by Tuesday afternoon, with 365 to communications watchdog Ofcom and another 130 to ITV.

The music mogul ordered an investigation, having been unaware that there was a third dog in the act, and while his fellow judges David Walliams, Alesha Dixon and Amanda Holden have stayed silent over the furore, producers have apologised.

A source told the Sun: "He [Simon] is shocked and angry. He had no idea. He wants to know who is responsible. Heads could roll."

ITV boss Peter Fincham has called the presentation of Jules O'Dwyer's dog act a "judgement call" - as complaints poured in about the Britain's Got Talent stunt.

And Mr Fincham admitted that Britain's Got Talent should have made it clearer that champion O'Dwyer used a stunt double dog for her winning sketch.

He told campaign group the Voice of the Listener and Viewer (VLV) that the way the act was presented was "a judgment call".

But he added: "In the semi-final it was made quite clear the other dog played a role in it.

"In the audition it was made quite clear this was a dog act with a range of dogs.

Jules O'Dwyer and Matisse out and about in London (Image: Rex)

"In hindsight, in the final it would have been better if that was clear."

An Ofcom spokesman said that complaints will be assessed before a decision is taken on whether to investigate.

Last night O'Dwyer said that she was "shocked and surprised" by viewers' reactions.

The guide dog trainer, who beat Welsh choir Cor Glanaethwy and magician Jamie Raven to the £250,000 prize with a sketch involving a tightrope and stolen sausages, said she did not use Matisse, the dog which viewers believed performed the stunt, because he did not like heights.

"I was disappointed when people said I allegedly hid Chase and I was trying to make it like Chase was Matisse. That's not so," she said.

Jules claims she didn't intent to mislead anyone (Image: Splash)

"I introduced Chase in the semi-final, and I said Chase is Matisse's best mate. Why put the pressure on the dog when I already have another dog who can perform it on television?"

The sketch, which starred O'Dwyer as a policewoman going after "sausage thief" Matisse, also featured another of her pets, three-legged Skippy.

O'Dwyer added: "I know my dogs, and I know what they are comfortable with. I'm not hiding anything. Skippy was a secret - I wanted to keep him a secret because that was the emotional factor and we hadn't introduced him before."

There was no sign of Chase, who had previously appeared in the semi-final, when O'Dwyer and Matisse took to the stage to be congratulated on their win by the judges and hosts Ant and Dec.

Their prize includes a spot at this year's Royal Variety Performance.

More than 13 million viewers watched O'Dwyer and Matisse become the second dog act to win Britain's Got Talent, following Ashleigh Butler and Pudsey in 2012, in the highest rating final since that year.

Did you tell the difference?

Voting figures showed that O'Dwyer and Matisse won by just 2% - getting 22.6% of votes compared with 20.4% for magician Raven.

Outraged viewers claimed to be "misled" over Matisse on the tightrope stunt.

Rachel Louise wrote: "How can BGT allow a stunt double for the dog and try to hide it, shouldn't be allowed to be the winner!"

Niamh Skinner said: "I've just been informed that Matisse had a stunt double doing the tightrope walk. Absolutely fuming. I voted for that dog!"

Andrea Foreman wrote: "I think they should step down and give it to the magic man."

But others described the furore as a storm in a teacup.

Video Loading

Video Unavailable

Click to playTap to play

The video will start in 8Cancel

Play now

Mike Ward wrote: "So she trained more than one dog to be brilliant? Seriously, what's the problem?!"

A spokesman for the producers of Britain's Got Talent said: "The audience had previously seen from Jules's semi-final routine that she works with a second dog, Chase, alongside Matisse. For the final performance, as Jules has said publicly herself, Chase completed the tight-rope walking section of the act.

"During the competition viewers have seen that Jules's act involves a team of dogs, including Chase and Skippy, alongside starring dog Matisse, to perform her unique mixture of dog agility and story-telling. We are sorry if this was not made clearer to the judges and viewers at home during their final performance."